Existing wavelength division multiplexed (WDM) networks create point-to-point communication channels between two nodes, which is wasting bandwidth if the connection requires less than a full wavelength of bandwidth.
Existing networks also use time-division multiplexing (TDM) or packet-based architectures such as Ethernet or resilient packet ring (RPR) to share a wavelength between nodes. This solution requires optical to electrical to optical conversion at each node of the wavelength being shared. This solution limits the bandwidth that can be added at each node because transit traffic must be processed by the transponder, exhausting available add/drop bandwidth.
Digital coherent detection is considered as a promising technique for future high-speed optical transmission because of its high receiver sensitivity and capability to compensate for transmission impairments such as chromatic dispersion (CD) and polarization-mode dispersion (PMD), which critically impact the performance of high-speed transmission. While 100-Gb/s Ethernet is currently being researched and developed for next-generation optical transport systems, Terabit/s Ethernet has already been mentioned as a future direction for optical transport systems.